On the Causal Virus of Tomato Streak Disease and its Mutants

Abstract

A strain of TMV, LFD-St (=Lycopersicon fruit deforming streak strain) was isolated from an immature fruit of a streak-diseased tomato plant which showed convex irregular green rings, 1∼2cm in diameter, on the surface. In tomato this strain caused dark brown necrotic streaks along the veins on the undersides of the leaves and then these streaks developed on the petioles and the stem. The leaves showed interveinal necrotic spots and sometimes mosaic symptoms. Samsun tobacco produced necrotic local lesions on the LFD-St-inoculated leaves generally, but sometimes necrotic oak leaf patterns which surrounded the midrib and the larger veins of the inoculated leaves, instead of distinct local lesions. LFD-St caused also necrotic lesions on the inoculated leaves of many other tobacco cultivars, Nicotiana species, petunia, and Chenopodium amaranticolor. No local and systemic symptoms were produced on LFD-St-inoculated Phaseolus vulgaris. In tomato plants the infection of LFD-St was cross-protected by the preinoculation of L₁₁A, an attenuated tomato strain of TMV. Samsun tobacco which produced necrotic local lesions by the inoculation of LFD-St showed often mild mosaic on the upper leaves from about 20 days to one month after inoculation. From such upper leaves a strain of TMV, LFD-1, was isolated. Other two strains of TMV, LFD-2 and LFD-3, were also isolated from Bright Yellow and Samsun tobacco, respectively, which had been inoculated originally with local lesion isolates of LFD-St. LFD-1 caused only local lesions on Bright Yellow tobacco, and LFD-2 local lesions followed by systemic necrotic and chlorotic lesions. LFD-3 caused severe mosaic on Samsun tobacco, local lesions and systemic mosaic symptoms on Bright Yellow tobacco, and necrotic local lesions on Phaseolus vulgaris. These three strains caused mosaic symptoms but no necrosis on tomato plant. LFD-St was inactivated by dilution between 10^-5 and 10^-6, and in ten min. at 90C. The dilution end points of LFD-1, -2, and -3 were between 10^-8 and 10^-9. The virus particles of these four strains were 300nm long and rod-shaped like the OM strain of TMV.